	June 30, 2021		December 31, 2020
Assumed gathering, processing and transportation contracts	$	474	$	—
Pension and postretirement benefit obligations		227		243
Commodity derivatives		157		5
Restructuring and transaction costs		122		137
Estimated future obligation under a performance guarantee		95		—
Other		173		166
Total other long-term liabilities	$	1,248	$	551

Devon assumed fixed gathering, processing and transportation contracts in the Merger and recognized a liability related to the difference in the contractual and market rates of these contracts as of the date of the Merger. The terms of the contracts extend through 2038 and all relate to the Delaware Basin. This difference will be recognized as a reduction to production expenses as the associated reserves are produced over the life of the respective contracts. For the six months ended June 30, 2021, Devon recognized $16 million of non-cash amortization of these liabilities as a reduction of production expenses in the consolidated statements of comprehensive earnings.

Additionally, in the Merger, Devon assumed a future obligation under a performance guarantee related to gathering and processing commitments for assets WPX sold in 2018 in which the purchaser of those assets is now not expected to have the financial

ability to satisfy the obligations. As of June 30, 2021, Devon recorded a $129 million liability for the estimated potential exposure based on probability-weighted cash flows for the remainder of the contract term of five years. Of the $129 million, $95 million is included in other long-term liabilities and $34 million is included in other current liabilities on the consolidated balance sheets as of June 30, 2021.